Lightweight aggregate furnace patch lining and process of applying



, R. F. GIBSON ETAL LIGHTWEIGHT AGGREGATE FURNACE PATCH LINING Sept. 15, 1959 AND PROCESS OF APPLY Filed Nov. 28, 1950 FIG.2

INVENTOR5 A F o L D R F GIBSON ATTORNEY United States Patent LIGHTWEIGHT AGGREGATE FURNACE PATCH LINING AND PROCESS OF APPLYING Richard F. Gibson, Albemarle, N.C., and Albert Floyd Old, Bremo Bluff, Va., assignors to Southern Lightweight Aggregate Corporation, Richmond, Va.

Application November 28, 1955, Serial No. 549,484 2 Claims. (Cl. 25-155.5)

This invention relates to concretes "and more particularly to a lightweight aggregate concrete mix especially adapted for filling or patching holes in furnace or kiln linings and to an improved process for accomplishing this and producing an improved concrete.

Kilns, particularly those of the rotary type, are frequently in continuous operation on a twenty four hour seven day week basis and are used for many purposes well known in the art, requiring the application of heat to substantially continuously flowing raw materials of various kinds.

These raw'materials are usually rough in texture, and theirmovement, including tumbling, through the kiln in combination with the high temperatures used tends to erode the linings by mechanical abrasion, thermal stresses and chemicalinteraction.

Although the lining material is selected for its superiority in resisting such'forces, nevertheless, portions of it fail as a result of the factors mentioned so that it becomes necessary from time to time to replace all or portions of the lining.

Heretofore, the repair of lining areas of limited size has usually necessitatedshut down of the kiln for a sufiicient length of time for it to cool in order that workmen might enter and replace. the lining which has been lost or needs repair. Since kilns are oftentimes of large size such as eight feet in diameter and over one hundred feet long and the linings are thick, and in view of the temperatures-used (oftentimes-exceeding 2000" F.) the time of shut down has been 'quite substantial. The substantial loss of productive output in addition to the fuel required to bring the kiln back to operating temperature has made the cost of such repairs large. A further factor is that because of the nature of the material available for patching or filling the voids, it has been necessary to apply these while the kiln is relatively cool and to permit them to cure or set up a substantial time prior to refiring of the kiln.

Accordingly, it is an object of the present invention to provide an improved concrete material having high abrasion resistance and low thermal conductivity characteristics.

A further object is to provide material which may be applied to fill in voids in kiln linings without waiting for the kiln to cool and which possesses superior characteristics.

A further object is to provide an improve method for patching or filling voids in kiln linings through the use of the improved matreial of the present invention.

These and other objects of the present invention will become apparent from the following description in con junction with the accompanying drawing in which Fig. l is a fragmentary perspective of an end of a kiln with a hole in its lining and with a patch applied according to the present invention (a portion being removed for clarity of presentation),

' patch; and

"ice

2 Fig. 2, an enlarged section through the material of a Fig. 3, a perspective, to an enlarged scale, of a portio of the surface of a part of the kiln wall illustrating the. method of installing cleats from the exterior of the kiln. Various materials have been used for kiln linings, both in monolithic and block or brick form. Among the desirable characteristics which lining materials should p0s sess are those of high resistance to mechanical abrasion and low thermal conductivity. Lining materials vary' rather widely in these characteristics.

Conventional lining materials heretofore known such as brick or ordinary concrete must be applied and per-. mitted to cure without being subjected to thermal shock. For example, the application of excessive heat to concrete formed from materials such as quartz sand and gravel causes concrete to disintegrate.

' patching without waiting for the kiln to cool.

According to the present invention, lightweight aggre-' gate having particular characteristics may be used together with certain cements such as Portland, slag 'or natural, and applied to the area of the kiln requiring sulting material is at least equal to and superior to many kiln lining materials with respect to abrasion resistance and thermal conductivity. Furthermore the material of the patch usually stays in place longer than ordinary kiln brick; it has been found upon examination of the patch ing material after shutdown of the kiln for the replacement of the lining that such material has maintained a hard smooth surface and is more firmly adhered to the kiln wall than the surrounding lining.

- In producing the patching material, the lightweight aggregates referred to in our Patent 2,721,069 havebeen found to be especially efficacious. The aggregates there described are adapted for load bearing concretes and are produced from slates. For use in the present inven tion, these are graded by sieve analysis as described hereafter. One of these aggregates results from the expansion of a weathered argillaceous slate which has lain close to the surface of the earth for a substantial period of years and during this time has been subjected to repeated cycles of freezing and thawing, to erosion, and

has been permeated to some degree with substances such as clay or silt that has flowed down into the voids. result has been that the cleavage lines or planes have been broken or displaced. As a result when such material is graded to the desired size for heat treatment the individual particles are substantially free of cleavagelines.

The other aggregate described results from the heat The lightweight aggregate used as the aggregate in the material of the present invention is obtained as a result 7 of the kiln heat treatment described in Patent 2,721,069.

Following such kiln heat treatment, the aggregate is crushed and for the purposes of the present invention is sized or graded according to the following sieve analysis based on the American Society of Testing Materials specification:

Test batches of concrete are made using Portland cement or equivalent (such as natural or slag cement) and The 'Whenuan eroded area or void is found in the kiln, it,

is only necessary to stopoperation of the: kiln sufiiciently long to apply thepatchto the area. The kiln is rotated tol'b'ring the area on to the lower side preferably so that,

the may flow by gravity into the void. If the area isbeyon'dreach from the end of the kiln by ordinary means, a pipe or the like may be used to convey themate'rial to the area. Because of the heat present, the cement hardens almost immediately, the resultbeing that operation of the kilnmay be resumed as soon as the materialis in place.

The abrasive resistance of the patching material is higherfthan that of brick ordinarily used; and stays in place 3to 5 times longer than ordinary brick. Similarly the K factor? is lower than that of such brick and runs between 3.5-4.0 B. t.u. per hour per square foot per inch of""'thickness.

The foregoing method of patching is suitable for relatively'small areas up to approximately 3 to 4 square feet. For larger areas it is preferable to weldcleats or rods or, similar type projections to the interior ofithe shell" to assist in retaining the patching material in place. Iftime and conditions permit, the projections maybe attached by welding from the interior. procedure, however, requires that the temperaturcbe siifiiciently low for'a workman to work within the kiln.

Inorder to avoid the delay required for cooling of the kiln, the followingldescribed method'may be used. Refe'rring more particularly to Fig. l, a kiln is illustrated having alining 11 of blocks or brick 12 adjacent to the end '13; In the end portion, there is a void 14 with patching materiallS, shown in place at the rear portion thereof for illustrative purposes. Cleats 16 are welded tothe shell 17 of the kiln and project inwardly. The illustrated cleats are angle iron welded in the designated place by cutting openings 18 with a torch or the like through which the cleats may project into the interior of the kiln, the openings being cut from the outside. After cutting of the openings the cleats are inserted therethrough and the end portions 19 joined by a weld 20 to the shell. As soon as the desired number of cleats are positioned, the batch of material may be poured into thelocation and operation of the kiln resumed.

It' will be understood that cleats may be installed .as

described'at a location in the kiln remote from its ends, and without requiringa workman to enter the kiln or be exposed to the temperatures therewithin. Of course, such cleats may be installed from within if the furnace is shut down. The concrete'mix may be applied to the area, by conventional means such as long handled shovels, pipes, and the like.

Althoughthe invention has been described in connection with the use of expanded lightweight aggregates produced from argillaceous and non-argillaceous slates, it is This believed that expanded lightweight aggregates produced from shalcs and clays may also be used.

Accordingly it will be understood that an improved concrete mix has been provided which may be poured onto a hot surface such as in a kiln, although its use is not so limited, and which withstands such heat without the necessity of slow curing, as with conventional mixes. The material provides a hard abrasion resistant patch; having low thermalconductivity and a: high' degree of adherence to. the wall; of thev kiln.

Although particulan applications have. been descn'bed, it will be. understoodby those-skilled in-the'art that the invention is notthus limited, but that equivalentmaterials and applications are within the scope of the invention and, therefore, the invention is only. limited as defined in the following claims.

What is claimed is:

. 1. The method of filling avoid in-kiln lining resulting from theremoval of. the lining by erosion, cracking, and the like, comprising preparing, a: concrete mix-using, approximately, 5 /2 to 7 bags oftcement per. cubic yardof concrete mix together 'With lightweight aggregate pre-- pared from expanded particles of, slate,. thewater/ cement ratio being in the range. ofapproximately 3. to.1 to 5.to. 1,, preparing the area of; the void for the. mix comprising. cutting a plurality of. openings from, the. exterior. of the: kiln wall through thekiln wall, suchopeningacorre. sponding to the profile of projecting members, insertinga projecting member through each. opening and retaining the tip of. the projecting, member. in.contiguo,us. relation. to the opening by, the. application of a:v weld between. such, end and .the pprtionof thewall. defining, the-open" 4 ing, and pouring the mix into thevoid while-thekiln is hot.

2. The method of filling avoid in kiln liningresulting. from thev removakof thelining by; erosion,- cracking and the like, comprising preparing; a. concrete mix, preparing the area of the void for the mixcomprising; cut ting a. plurality of openings from the-exterior of, the kiln wall through the kiln wall, such.openings. corresponding to the profileofprojecting members, inserting. a projecting member from saidexterior. througheach opening and retaining .the,.-tip of the projecting-.member in contiguous relation .to the, opening by the application-'- of a Weld from-said exterior between such end and the. portionofthewall defining the opening, and pouring, the mixinto the .void .in contact with the portions of. the; projecting members. extending, thereinto.

References Cited inthe file ofthis patent.

UNITED STATES PATENTS' 1,091,567 Eldred Mar.' 31, 1914.v 1,316,298 Gold Sept. 16,. 1919, 1,916,157 Chappell June 27, 1933. 2,124,865 Winkler 6138.1. July 2 1938 2,358,652 Nicholas Sept. 19', 1944 2,504,185 Debenham Apr. 18, 1950: 2,564,009- Hyche Aug. 14; 1951 2,607,700 Vail Aug. 19; 1952' 2,635,865: Brumbaugh Apr. 21, 1953 

